This invention relates to 4:1 baluns.
The construction of 4:1 baluns using coaxial cable or twisted pair transmission lines is known in the art, and is illustrated on page 344 of "The Radio Amateur's Handbook", published by The American Radio Relay League in 1961, which details practical considerations and design techniques for baluns using coaxial cable and twisted pair lines.
One application in which baluns are used is impedance matching of broadband circuits for transmitters and receivers that operate in frequencies up to the megahertz range. For the design application, reference can be made to an article entitled "Designing Toroidal Transformers to Optimize Wideband Performance" by Herbert L. Krauss and Charles W. Allen, published in Electronics, Aug. 16, 1973, pp. 113-116. In the article, there is disclosed the use of toroids and twisted pairs for designing transformers which have impedance ratios of 4:1.
A prior art balun is shown in FIGS. 1a and 1b. In FIG. 1a, there are two conductors which may be coaxial wires or twisted pairs 1 and 2. Conductor 1 has an A terminal on one end and an A1 terminal on the other end, and conductor 2 has a terminal B on one end and terminal B1 on the other end. In FIG. 1b, the conductors 1 and 2 are arranged in a balun configuration which is terminal B being joined to terminal A1 and terminal B1 being connected to the reference plane 3. An input signal is applied across terminal A and the reference plane, and the output signal is removed from terminal A1 and the reference plane. The impedance of the balun of FIG. 1b is the characteristic impedance Z.sub.o of the twisted pair wire or coaxial cable used.